The Amp Hour Electronics Podcast

#228 – An Interview with Shahriar from The Signal Path – Quisquous Quivering Quadripole


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The Amp Hour Electronics Podcast

The Amp Hour (Chris Gammell and David L Jones)

Description: Keep Current

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#228 – An Interview with Shahriar from The Signal Path – Quisquous Quivering Quadripole

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Welcome the YouTube channel.

  • Shahriar currently works in the ASIC design lab that is part of the Murray Hill building at Bell Labs.
  • The millimeter wave researchers often say “GHz is basically DC”
  • Making higher speed complex devices can be difficult but there was a 2006 paper that had a 81Gb/s timer.
  • ST Micro has one of the leading SiGe BiCMOS high speed.
  • The ASIC group has some of their research work fabricated at TowerJazz because it is approved by the government.
  • The government has been focused on GaAs, GaN
  • The PA/front end of cellphones/wifi uses GaAs (instead of Si) because of breakdowns of submicron processes.
  • Chip designers get design kit from the fab and these are used in simulations. Here is an example of one from TSMC, provided by MOSIS (discussed previously on the show)
  • Shahriar usually tests new design kits with a LNA/PA.  He also designed a 160 GHZ PLL as a student.
  • 3 um x 3 um capacitor is 12 fF.
  • The ASIC designers use Cadence.
  • Design kits will have variations: DC characteristics like transconductance (gm) might be ok but the designers know the capacitance will have uncertainty as they characterize the design kit more.
  • Dave recently did an EEVblab about what a hobbyist should know. Shahriar agrees and things knowing to test is very important.
  • Chris loved Shahriar’s cryo experiments because they really showed the (extreme) effect of temperature on components.
  • Testings for THz can require complex/custom test gear. Often it is a network analyzer with a front end. Keysight.
  • One Signal Path episode used a Keysight/Agilent 62GHz oscilloscope, it was on loan from the dealer.
  • On scopes you start to run into the noise floor of the ADC (b/c jitter). This limits around 100 GHz. At 110GHZ the connectors become limiting (1 mm). If the connectors go to .8 mm, it could go up to 160 GHz.
  • Shahriar has a range of research papers:
  • Peer review is critical for journals. Bell Labs splits research between keeping it private and publishing it.
  • There are a range of technical conferences for millimeter wave research: IMS conference
  • A phased array is a grid of antennas. It allows steering the signals towards the source/receiver.
  • Different high GHz bands are great because of the open bandwidth.

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